The present invention relates to puncture resistant insoles for boots and other shoes.
Manufacturing, construction and demolition sites are often full of sharp objects such as protruding nails which present a significant hazard to unwary workers. When stepped on, upturned nails in a board or the like easily penetrate the worker's boot and foot causing considerable pain and injury. Such a puncture wound can hobble a worker for weeks and requires particular medical attention to avoid tetanus or other anaerobic bacterial infections.
The current OSHA puncture hazard requirement is being met by the incorporation of a steel or metal insole in worker footwear. The use of metal insoles presents several problems and has several undesirable characteristics. In particular, metal is, by its nature, relatively inflexible and stiff. The use of footwear which is inflexible or stiff causes workers to be unable to flex their feet when walking, climbing, or working on difficult, uneven surfaces. As a result, the wearer is subject to falling, stumbling, and slipping. In short, there is a substantial loss of sure-footedness when wearing the present puncture resistant footwear.
The metal in currently available puncture resistant footwear conducts both electricity and heat. Workers who wear footwear containing a steel insole are, thus, more subject to frostbite when working in cold environments. Further, footwear with metal insoles cannot be worn by electrical workers. Instead, a non-conducting fiberglass insole is required for those engaged in electrical work. Fiberglass manufacturing processes, however, are subject to numerous environmental issues, which tend to increase the cost of fiberglass. Moreover, the fiberglass insole must be quite thick to provide the required puncture resistance, which reduces both the comfort and flexibility of the shoe.
Insoles have been developed which comprise multiple layers of stacked fibrous materials or fabric which are bonded together by synthetic resins and the like to form resin impregnated laminates. Fibrous materials previously identified as useable include spun glass fibers or nylon. Impregnation of the fabric is indicated as necessary to provide the desired puncture resistance. However, the resin impregnation process adds to the cost of materials and labor, reduces flexibility of the resulting insole and generally adds to the overall thickness of the insole.
Any puncture resistant insole which appreciably decreases the flexibility of the footwear or which is too thick is uncomfortable for workers to wear, and workers will remove the puncture resistant footwear when supervisors or regulators are not present. In addition, many workers wear the safety shoes only when doing jobs requiring the safety shoes and then change to more comfortable shoes when they are not needed. A more comfortable shoe would make these changes unnecessary and, as a consequence, reduce worker downtime.
There remains a need for a way to increase the puncture resistance of boots and the like without sacrificing comfort and flexibility or significantly increasing the weight of the boot.